How is an electric boiler's runaway risk different from a gas-fired boiler? Either could runaway in temperature (hell even a hot water heater can) but only if multiple controls have failed. The SlantFins even come with outdoor reset control, if you want it for a higher comfort constant flow setup. If the internal controls scare you, inserting a high-limit aquastat on the output piping to interrupt it may be cheap insurance, but not necessary. They come with the usual 3rd party test ratings for hydronic boilers, including ASME (which isn't often the case for hot-water heaters.)
I'd never design ANY heating system for 180F water, but Wirsbo has a test setup that's been running a length of PEX for over 25 years at elevated temp and pressure beyond the rated spec. An excursion to 200F isn't going to be a disaster with anybody's PEX, but 220F might if the pressure relief fails. Wirsbo rates theirs at 200F @ 80psi, an insane temp & pressure for radiant floor applications. "Brand X" PEX is often only rated at 180F nominal operating temp, but it can take much more at typical heating system pressures.
But I s'pose with an idiot system designer it's possible to defeat about any safety or temperature limit spec.
Electric boilers are relatively simple-minded & rugged beasts, and they're cheap. But even in nickel a kilowatt-hour land, in an upstate NY climate the total seasonal energy requirements it won't be ultra-cheap to operate. The boiler in question is likely to be more than 2x oversized for the load too, which is never a good idea for comfort and equipment longevity. Money spent on it is better spent elsewhere:
A 1.5-2.5 ton inverter-drive ductless air source heat pump (mini-split) appropriately sized for the heating load would pay for itself in under 5 heating seasons even with nickel electricity (and that's at the full installed price of the heat pump not some delta between an electric boiler installation and a mini-split.) Going with an electric boiler and NOT a mini-split would only make sense if you were willing to pay for the extra comfort-cush of a radiant floor or something. A heat pump with some cheap resistance electric backup for the sub-zero peak loads makes more sense otherwise. It would have have half (or less) the operating cost of an electric boiler during mid-winter, and less than 1/3 the operating cost during the spring & fall. In a ~7000 heating degree day climate those are significant savings.